Variable response to the diepoxybutane test in two dizygotic twins with Fanconi's anemia and flow cytometry for diagnosis confirmation

Comparison of the clinical phenotype and haematological course of siblings with Fanconi anaemia

Fanconi anaemia (FA) is a genetic disorder due to mutations in any of the 22 FANC genes (FANCA-FANCW) and has high phenotypic variation. Siblings may have similar clinical outcome because they share the same variants; however, such association has not been reported. We present the detailed phenotype and clinical course of 25 sibling sets with FA from two institutions. Haematological progression significantly correlated between siblings, which was confirmed in an additional 55 sibling pairs from the International Fanconi Anemia Registry. Constitutional abnormalities were not concordant, except for a moderate degree of concordance in kidney abnormalities and microcephaly.

Genotype-phenotype correlations in Fanconi anemia

Although still incomplete, we now have a remarkably detailed and nuanced picture of both phenotypic and genotypic components of the FA spectrum. Initially described as a combination of pancytopenia with a limited number of physical anomalies, it was later recognized that additional features were compatible with the FA phenotype, including a form without detectable malformations (Estren-Dameshek variant). The discovery of somatic mosaicism extended the boundaries of the FA phenotype to cases even without any overt hematological manifestations. This clinical heterogeneity was augmented by new conceptualizations. There was the realization of a constant risk for the development of myelodysplasia and certain malignancies, including acute myelogenous leukemia and squamous cell carcinoma, and there was the emergence of a distinctive cellular phenotype. A striking degree of genetic heterogeneity became apparent with the delineation of at least 12 complementation groups and the identification of their underlying genes. Although functional genetic insights have fostered the interpretation of many phenotypic features, surprisingly few stringent genotype-phenotype connections have emerged. In addition to myriad genetic alterations, less predictable influences are likely to modulate the FA phenotype, including modifier genes, environmental factors and chance effects. In reviewing the current status of genotype-phenotype correlations, we arrive at a unifying hypothesis to explain the remarkably wide range of FA phenotypes. Given the large body of evidence that genomic instability is a major underlying mechanism of accelerated ageing phenotypes, we propose that the numerous FA variants can be viewed as differential modulations and compression in time of intrinsic biological ageing.

Fanconi's anemia in monozygotic twins

Fanconi's anemia is one of the inherited causes of bone marrow failure. It is inherited in autosomal recessive fashion. It presents as aplastic anemia usually at the age of 7-8 yr. Leukemias and solid tumours are complications in those who manage to survive beyond two decades. Though it has been seen in siblings, reports in monozygotic twins have been very few.

Fanconi anaemia and leukaemia - clinical and molecular aspects

Fanconi anaemia (FA) is an autosomal recessive chromosomal instability disorder, which is characterized by congenital abnormalities, defective haemopoiesis and a high risk of developing acute myeloid leukaemia and certain solid tumours. It can be caused by mutations in at least eight different genes. Molecular studies have established that a common pathway exists, both between the FA proteins and other proteins involved in DNA damage repair such as NBS1, ATM, BRCA1 and BRCA2. This review summarizes the general clinical and specific haematological features and the current management of FA. Recent molecular advances will also be discussed in the context of the cellular and clinical FA phenotype, with particular emphasis on the haematological aspects of the condition.

Fanconi anaemia

Fanconi anaemia (FA) is an autosomal recessive disease characterised by congenital abnormalities, defective haemopoiesis, and a high risk of developing acute myeloid leukaemia and certain solid tumours. Chromosomal instability, especially on exposure to alkylating agents, may be shown in affected subjects and is the basis for a diagnostic test. FA can be caused by mutations in at least seven different genes. Interaction pathways have been established, both between the FA proteins and other proteins involved in DNA damage repair, such as ATM, BRCA1 and BRCA2, thereby providing a link with other disorders in which defective DNA damage repair is a feature. This review summarises the clinical features of FA and the natural history of the disease, discusses diagnosis and management, and puts the recent molecular advances into the context of the cellular and clinical FA phenotype.